When a semiconductor circuit is manufactured it is necessary to form a plurality of via cavities between individual layers of the semiconductor circuit in order to provide conduits for electrical communication between metal layers of the semiconductor circuit. In order to facilitate the efficient filling of the via cavities with metal fill material (e.g., aluminum) the sidewalls of the via cavities should have an appropriately shaped profile. That is, the shape of a via cavity should not interfere with a subsequent via fill process.
Prior art methods of forming a via cavity, however, often leave one or more sharp edges in the sidewall profile of the via cavity. Other prior art methods of forming a via cavity create via cavity sidewalls that have a concave profile. The prior art improves the line-of-sight metal deposition into the via holes compared to a completely vertical sidewall produced by anisotropic via etching. However, the demands on metal deposition into submicron geometry via holes in use today require more than just line-of-sight deposition. The aluminum must be deposited at a high temperature to allow the aluminum to flow into the vias and provide low resistance electrical pathways.
The presence of sharp edges or the presence of a concave profile in a via cavity sidewall tends to impede the flow of the fill material and cause the fill process of via cavity to be incomplete. That is, voids in the fill material may be caused by the sharp edges in the sidewalls of the via cavity. Voids in the fill material may also be caused by the presence of a concave profile in the sidewalls of the via cavity.
Therefore, there is a need in the art for a system and method that is capable of providing a via cavity in a semiconductor circuit that has an optimally shaped sidewall profile. There is also a need in the art for a system and method that is capable of providing a via cavity having a sidewall profile that facilitates a subsequent via fill process.